(a) Technical Field
The present invention relates to a lithium ion-sulfur battery. More particularly, it relates to a structure of a lithium ion-sulfur battery which can be applied to a next-generation electric vehicle and improve charge/discharge durability.
(b) Background Art
In 1991, a lithium-ion secondary battery using an intercalation reaction was developed and industrialized. In response, the lithium-ion secondary battery has attracted much attention in the automotive industry including hybrid vehicles, plug-in hybrid vehicles, electric vehicle, etc. as well as in the battery industry itself.
As shown in FIG. 1, the lithium-ion battery has a structure, in which carbon or graphite is used as a negative electrode 1 and a lithiated transition metal intercalation compound is used as a positive electrode 2, the negative electrode 1 and the positive electrode 2 being connected by an electric circuit. During use of the lithium-ion battery, lithium ions 5 move between the positive electrode 2 and the negative electrode 1 to be intercalated into or deintercalated from the carbon material to repeat charge and discharge cycles.
The lithium-ion battery uses the carbon material as the negative electrode 1 to improve charge/discharge efficiency.
Reference numerals 3 and 4 denote a separator membrane and an electrolyte, respectively.
However, the existing lithium ion battery has a theoretical energy density of 570 Wh/kg and a maximum density of 120 Wh/kg at the current level, which is insufficient to run about 500 km, a running distance per charge of an internal combustion engine vehicle.
Therefore, the development of a battery for a next-generation vehicle having a higher energy density than the existing lithium-ion battery is required.
A lithium-sulfur battery has been studied as one of the candidates for next-generation vehicle batteries.
As shown in FIG. 2, the lithium-sulfur battery is a galvanic cell using an organic or inorganic electrolyte 4, in which lithium metal is used as a negative electrode 6 and sulfur is used as a positive electrode 7 to repeat charge and discharge cycles by an oxidation-reduction reaction. The lithium-sulfur battery has a low manufacturing cost and a high energy density (e.g., 2,600 Wh/kg).
The initial capacity of the lithium-sulfur battery is very high because the lithium metal is used as the negative electrode 6. However, as the charge/discharge cycles are repeated, dendrite 8 is deposited on the surface of the metal, thereby reducing the charge/discharge efficiency and safety.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.